<!DOCTYPE HTML>
<html>

<head>
    <style type="text/css">
        #div1,
        #div2 {
            /* float: left; */
            display: flex;
            width: 100px;
            height: 100px;
            margin: 10px;
            padding: 10px;
            border: 1px solid #aaaaaa;
        }

        img {
            height: 100px;
            width: 100px;
        }
    </style>
    <script type="text/javascript">
        function allowDrop(ev) {
            ev.preventDefault();
        }

        function drag(ev) {
            ev.dataTransfer.setData("Text", ev.target.id);
        }

        function drop(ev) {
            ev.preventDefault();
            var data = ev.dataTransfer.getData("Text");
            ev.target.appendChild(document.getElementById(data));
        }
    </script>
</head>

<body>

    <div id="div1" ondrop="drop(event)" ondragover="allowDrop(event)">
        <img src="./image/tx9.png" draggable="true" ondragstart="drag(event)" id="drag1" />
    </div>
    <div id="div2" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
    <img src="./image/tx5.png" draggable="true" ondragstart="drag(event)" id="drag2" />
</body>

</html>